Summary of Significant Accounting Policies and Other Information (Policies)	3 Months Ended
Mar. 31, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Consolidation	The consolidated financial statements include the accounts of Power Solutions International, Inc. and its wholly-owned subsidiaries and majority-owned subsidiaries in which the Company exercises control. The consolidated financial statements were prepared in accordance with generally accepted accounting principles in the United States (“U.S. GAAP”) and rules and regulations of the SEC for interim financial reporting. All intercompany balances and transactions have been eliminated in consolidation.
Basis of Presentation	Certain information and note disclosures normally included in the Company’s annual financial statements prepared in accordance with U.S. GAAP have been condensed or omitted. The accompanying unaudited Consolidated Financial Statements have been prepared in accordance with the instructions to Form 10-Q and include all of the information and disclosures required by U.S GAAP for interim financial reporting. These unaudited Consolidated Financial Statements should be read in conjunction with the Consolidated Financial Statements of the Company and related footnotes for the year ended December 31, 2025, included in the 2025 Annual Report on Form 10-K, filed with the SEC on March 2, 2026 (the “2025 Annual Report”). There have been no material changes in the Company’s significant accounting policies as compared to the significant accounting policies described in the Company’s 2025 Annual Report. The accompanying interim financial information is unaudited; however, the Company believes the financial information reflects all adjustments (consisting of items of a normal recurring nature) necessary for a fair presentation of its financial position, results of operations and cash flows in conformity with U.S. GAAP. Operating results for interim periods are not necessarily indicative of annual operating results.
Segments	Segments The Company operates as one business and geographic operating segment. Operating segments are defined as components of a business that can earn revenues and incur expenses for which discrete financial information is available that is evaluated on a regular basis by the chief operating decision maker (“CODM”). The Company’s CODM is its principal executive officer, who decides how to allocate resources and assess performance. A single management team reports to the CODM, who manages the entire business. The Company’s CODM reviews consolidated statements of income to make decisions, allocate resources and assess performance, and the CODM does not evaluate the profit or loss from any separate geography or product line.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires that management make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. Significant estimates and assumptions include the valuation of allowances for uncollectible receivables, inventory reserves, warranty reserves, stock-based compensation, evaluation of goodwill, other intangibles, property, plant and equipment for impairment, income tax valuation allowances and determination of useful lives of long-lived assets. Actual results could materially differ from those estimates.
Restricted Cash	Restricted Cash Restricted cash consists of funds that are contractually restricted as to usage or withdrawal due to required minimum levels of cash collateral for letters of credits and contractual agreements with customers.
Inventories	Inventories The Company’s inventories consist primarily of engines and parts. Engines are valued at the lower of cost, including estimated freight-in or net realizable value. Parts are valued at the lower of cost or net realizable value, except for integral parts provided by customers for installation on custom ordered engines. Such parts are accounted for as noncash consideration which is valued at fair value. Net realizable value approximates replacement cost. Cost is principally determined using the first-in, first-out method and includes material, labor and manufacturing overhead. It is the Company’s policy to review inventories on a continuing basis for obsolete, excess and slow-moving items and to record valuation adjustments for such items in order to eliminate non-recoverable costs from inventory. Valuation adjustments are recorded in an inventory reserve account and reduce the cost basis of the inventory in the period in which the reduced valuation is determined. Inventory reserves are established based on quantities on hand, usage and sales history, customer orders, projected demand and utilization within a current or future power system. Specific analysis of individual items or groups of items is performed based on these same criteria, as well as on changes in market conditions or any other identified conditions.
Warranty Costs	Warranty Costs The Company offers a standard limited warranty on the workmanship of its products that in most cases covers defects for a defined period. Warranties for certified emission products are mandated by the U.S. Environmental Protection Agency (the “EPA”) and/or the California Air Resources Board (the “CARB”) and are longer than the Company’s standard warranty on certain emission-related products. The Company’s products also carry limited warranties from suppliers. The Company’s warranties generally apply to engines fully manufactured by the Company and to the modifications the Company makes to supplier base products. Costs related to supplier warranty claims are generally borne by the supplier and passed through to the end customer. Warranty estimates are based on historical experience and represent the projected cost associated with the product. A liability and related expense are recognized at the time products are sold. The Company adjusts estimates when it is determined that actual costs may differ from initial or previous estimates. The Company’s warranty liability is generally affected by failure rates, repair costs and the timing of failures. Future events and circumstances related to these factors could materially change the estimates and require adjustments to the warranty liability. In addition, new product launches require a greater use of judgment in developing estimates until historical experience becomes available.
Recently Issued Accounting Pronouncements - Adopted and Recently Issued Accounting Pronouncements – Not Yet Adopted	Recently Issued Accounting Pronouncements – Adopted In July 2025, the FASB issued ASU 2025‑05, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses for Accounts Receivable and Contract Assets. The ASU provides a practical expedient that permits entities to assume that current economic conditions as of the balance sheet date will remain unchanged for the remaining life of current accounts receivable and current contract assets arising from transactions accounted for under Topic 606, Revenue from Contracts with Customers when estimating expected credit losses. The Company adopted ASU 2025‑05 effective January 1, 2026 and elected the practical expedient for its current accounts receivable and current contract assets. The adoption of this guidance did not have a material impact on the Company’s consolidated financial statements or related disclosures. Recently Issued Accounting Pronouncements – Not Yet Adopted In November 2024, the FASB issued ASU 2024-03, Income Statement - Reporting Comprehensive Income: Expense Disaggregation Disclosures (Subtopic 220-40). This update requires entities to provide more detailed disclosures about the components of significant expense categories, enhancing the transparency and decision usefulness of financial statements. The amendments in this update are intended to provide investors with additional information about specific expense categories in the notes to the financial statements at interim and annual reporting periods. The updated standard is effective for annual periods beginning after December 15, 2026, and interim reporting periods thereafter, although early adoption is permitted. While we anticipate that the adoption of this standard will require additional disclosures, the Company is currently assessing the impact of the amendment to this standard on its consolidated financial statements.
Fair Value of Financial Instruments	Current Assets Cash and cash equivalents (Level 1) are measured at carrying value, which approximates fair value because of the short-term maturities of these instruments. Debt The Company measured its material debt obligations and notes payable using original carrying value. •The fair value of the Revolving Credit Agreement approximated carrying value, as it is a variable rate loan. •The Company measured its non-interest bearing note payable using a rate which the Company could obtain financing of similar nature from other sources at the date of the transaction. The unamortized discount is reported in the Consolidated Balance Sheets as a deduction from the face amount of the note payable. •The Promissory Note was issued for the acquisition of MTL on January 9, 2026. The debt was established at market rate and the fair value approximates carrying value since the period of time between issuance and March 31, 2026 is not significant. •The Master Loan Agreements and the SBA Loan were part of debt assumed in the acquisition of MTL. The assumed debt is predominantly related to equipment loans which were issued within the past year and are third party agreements. The debt was recently established at market rates and is unlikely to have moved off market in the short period between the issuance in 2025 and March 31, 2026. Based on these factors, the fair value approximates carrying value.

Summary of Significant Accounting Policies and Other Information (Policies)

3 Months Ended

Mar. 31, 2026

Organization, Consolidation and Presentation of Financial Statements [Abstract]

The consolidated financial statements include the accounts of Power Solutions International, Inc. and its wholly-owned subsidiaries and majority-owned subsidiaries in which the Company exercises control. The consolidated financial statements were prepared in accordance with generally accepted accounting principles in the United States (“U.S. GAAP”) and rules and regulations of the SEC for interim financial reporting. All intercompany balances and transactions have been eliminated in consolidation.

Basis of Presentation

Certain information and note disclosures normally included in the Company’s annual financial statements prepared in accordance with U.S. GAAP have been condensed or omitted. The accompanying unaudited Consolidated Financial Statements have been prepared in accordance with the instructions to Form 10-Q and include all of the information and disclosures required by U.S GAAP for interim financial reporting. These unaudited Consolidated Financial Statements should be read in conjunction with the Consolidated Financial Statements of the Company and related footnotes for the year ended December 31, 2025, included in the 2025 Annual Report on Form 10-K, filed with the SEC on March 2, 2026 (the “2025 Annual Report”). There have been no material changes in the Company’s significant accounting policies as compared to the significant accounting policies described in the Company’s 2025 Annual Report. The accompanying interim financial information is unaudited; however, the Company believes the financial information reflects all adjustments (consisting of items of a normal recurring nature) necessary for a fair presentation of its financial position, results of operations and cash flows in conformity with U.S. GAAP. Operating results for interim periods are not necessarily indicative of annual operating results.

Segments

The Company operates as one business and geographic operating segment. Operating segments are defined as components of a business that can earn revenues and incur expenses for which discrete financial information is available that is evaluated on a regular basis by the chief operating decision maker (“CODM”). The Company’s CODM is its principal executive officer, who decides how to allocate resources and assess performance. A single management team reports to the CODM, who manages the entire business. The Company’s CODM reviews consolidated statements of income to make decisions, allocate resources and assess performance, and the CODM does not evaluate the profit or loss from any separate geography or product line.

Use of Estimates

The preparation of consolidated financial statements in conformity with U.S. GAAP requires that management make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. Significant estimates and assumptions include the valuation of allowances for uncollectible receivables, inventory reserves, warranty reserves, stock-based compensation, evaluation of goodwill, other intangibles, property, plant and equipment for impairment, income tax valuation allowances and determination of useful lives of long-lived assets. Actual results could materially differ from those estimates.

Restricted Cash

Restricted cash consists of funds that are contractually restricted as to usage or withdrawal due to required minimum levels of cash collateral for letters of credits and contractual agreements with customers.

Inventories

The Company’s inventories consist primarily of engines and parts. Engines are valued at the lower of cost, including estimated freight-in or net realizable value. Parts are valued at the lower of cost or net realizable value, except for integral parts provided by customers for installation on custom ordered engines. Such parts are accounted for as noncash consideration which is valued at fair value. Net realizable value approximates replacement cost. Cost is principally determined using the first-in, first-out method and includes material, labor and manufacturing overhead. It is the Company’s policy to review inventories on a continuing basis for obsolete, excess and slow-moving items and to record valuation adjustments for such items in order to eliminate non-recoverable costs from inventory. Valuation adjustments are recorded in an inventory reserve account and reduce the cost basis of the inventory in the period in which the reduced valuation is determined. Inventory reserves are established based on quantities on hand, usage and sales history, customer orders, projected demand and utilization within a current or

future power system. Specific analysis of individual items or groups of items is performed based on these same criteria, as well as on changes in market conditions or any other identified conditions.

Warranty Costs

The Company offers a standard limited warranty on the workmanship of its products that in most cases covers defects for a defined period. Warranties for certified emission products are mandated by the U.S. Environmental Protection Agency (the

“EPA”) and/or the California Air Resources Board (the “CARB”) and are longer than the Company’s standard warranty on certain emission-related products. The Company’s products also carry limited warranties from suppliers. The Company’s warranties generally apply to engines fully manufactured by the Company and to the modifications the Company makes to supplier base products. Costs related to supplier warranty claims are generally borne by the supplier and passed through to the end customer.

Warranty estimates are based on historical experience and represent the projected cost associated with the product. A liability and related expense are recognized at the time products are sold. The Company adjusts estimates when it is determined that actual costs may differ from initial or previous estimates. The Company’s warranty liability is generally affected by failure rates, repair costs and the timing of failures. Future events and circumstances related to these factors could materially change the estimates and require adjustments to the warranty liability. In addition, new product launches require a greater use of judgment in developing estimates until historical experience becomes available.

Recently Issued Accounting Pronouncements - Adopted and Recently Issued Accounting Pronouncements – Not Yet Adopted

Recently Issued Accounting Pronouncements – Adopted

In July 2025, the FASB issued ASU 2025‑05, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses for Accounts Receivable and Contract Assets. The ASU provides a practical expedient that permits entities to assume that current economic conditions as of the balance sheet date will remain unchanged for the remaining life of current accounts receivable and current contract assets arising from transactions accounted for under Topic 606, Revenue from Contracts with Customers when estimating expected credit losses. The Company adopted ASU 2025‑05 effective January 1, 2026 and elected the practical expedient for its current accounts receivable and current contract assets. The adoption of this guidance did not have a material impact on the Company’s consolidated financial statements or related disclosures.

Recently Issued Accounting Pronouncements – Not Yet Adopted

In November 2024, the FASB issued ASU 2024-03, Income Statement - Reporting Comprehensive Income: Expense Disaggregation Disclosures (Subtopic 220-40). This update requires entities to provide more detailed disclosures about the components of significant expense categories, enhancing the transparency and decision usefulness of financial statements. The amendments in this update are intended to provide investors with additional information about specific expense categories in the notes to the financial statements at interim and annual reporting periods. The updated standard is effective for annual periods beginning after December 15, 2026, and interim reporting periods thereafter, although early adoption is permitted. While we anticipate that the adoption of this standard will require additional disclosures, the Company is currently assessing the impact of the amendment to this standard on its consolidated financial statements.

Fair Value of Financial Instruments

Current Assets

Cash and cash equivalents (Level 1) are measured at carrying value, which approximates fair value because of the short-term maturities of these instruments.

Debt

The Company measured its material debt obligations and notes payable using original carrying value.

•The fair value of the Revolving Credit Agreement approximated carrying value, as it is a variable rate loan.

•The Company measured its non-interest bearing note payable using a rate which the Company could obtain financing of similar nature from other sources at the date of the transaction. The unamortized discount is reported in the Consolidated Balance Sheets as a deduction from the face amount of the note payable.

•The Promissory Note was issued for the acquisition of MTL on January 9, 2026. The debt was established at market rate and the fair value approximates carrying value since the period of time between issuance and March 31, 2026 is not significant.

•The Master Loan Agreements and the SBA Loan were part of debt assumed in the acquisition of MTL. The assumed debt is predominantly related to equipment loans which were issued within the past year and are third party agreements. The debt was recently established at market rates and is unlikely to have moved off market in the short period between the issuance in 2025 and March 31, 2026. Based on these factors, the fair value approximates carrying value.